1. Field of the Invention
The present invention relates to a developing apparatus used for so-called dip development for semiconductor wafers or the like.
2. Description of the Prior Art
One of the steps in fabricating semiconductor devices is a developing process of a resist film deposited on a surface of a semiconductor wafer (to be simply referred to as a wafer hereinafter).
Such developing apparatuses can be categorized into two types, i.e., one using a system of developing a plurality of wafers in a batch processing manner, and the other using a so-called continuous processing system. In the continuous processing system, wafers are sequentially conveyed one by one to the developing apparatus. For an automatic developing process, the type using the continuous processing system is advantageous over the one using the batch processing system.
The following two types have been mainly used as conventional developing apparatuses using the continuous processing system. One is a type using a spray system in which a developing solution is sprayed on a wafer. The other is a type using a paddle system in which development is performed by forming a paddle of developing solution on a wafer using a surface tension.
Demands have been recently arisen for high integration density of semiconductor devices. For this purpose, when a resist film is developed, an improvement in process precision is required, and a so-called aspect ratio (a ratio of the width of a pattern to which development can be performed to the depth of the pattern to which development can be performed) needs to be improved, as in dry etching after a developing ,process.
In order to meet such requirements, resist makers recommend using a developing solution containing an activator such as a penetrating agent and a surface protective agent. The solution containing the activator is very effective improving the aspect ratio. However, in some developing systems, if the developing solution containing the activator is used, uniform quality of resist films may not be obtained.
For example, in the developing apparatus of the spray system, a protective agent is precipitated on a portion where a high pressure is generated because of variations in spraying pressure of a developing solution on a wafer. As a result, dissolution delay locally occurs and a nondeveloped portion is locally formed.
On the other hand, in the developing apparatus of the paddle system, a paddle may not sufficiently formed because of a decrease in surface tension of the developing solution containing the activator.
Accordingly, especially in the case wherein development is performed using the developing solution containing the activator, the developing apparatus of the dip system is more effective, wherein a wafer is dipped in the developing solution.
FIG. 1 shows a developing apparatus of the continuous processing system using the dip system. Reference numeral 1 denotes an upper cup. Upper cup 1 is fitted in lower cup 2 to prevent scattering of a developing solution. Inner cup 3 is arranged in upper cup 1. Recess 3A is formed in inner cup 3 to define a dip tank for developing solution 11. An opening portion is formed at a central portion of inner and lower cups 3 and 2 to assure a path for allowing the vertical movement of spin chuck 7. In addition, residue drain pipe 4 communicating with recess 3A and wafer sealing vacuum pipes 5 are arranged in inner cup 3. Wafer sealing packings 6 are respectively arranged on end portions of vacuum pipes 5 so as to face recess 3A, thereby extending from a lower surface of recess 3A.
In the developing apparatus arranged in this manner, wafer 10 is held by suction on wafer sealing packings 6 by the effect of wafer sealing vacuum pipes 5. Upon suction of wafer 10, developing solution 11 is stored in recess 3A without leakage. More specifically, when development is to be performed, developing solution 11 is supplied to recess 3A in inner cup 3 through a nozzle or the like (not shown) arranged above wafer 10.
However, in such a developing apparatus, in order to form a dip tank for developing solution 11, developing solution 11 must be sprayed above wafer 10. As a result, since the spraying pressure of developing solution 11 is applied to wafer 10, defective development due to the spraying pressure cannot be prevented.